Freeze occurred after running Prime for hours on end, when I finally thought I had a stable system...
So I'm going to try at 1.40 in a while, can't really have my system dying on me right now so I'm running 1333MHz for the time being...
@RamGuy: do you suggest me bugging Asus about this? You know they don't respond well to Ram-related questions "Is it on the Vendor list? No? Then don't bother us..."